Prostacyclin derivatives are useful pharmaceutical compounds possessing activities such as platelet aggregation inhibition, gastric secretion reduction, lesion inhibition, and bronchodilation. Beraprost is a synthetic benzoprostacyclin analogue of natural prostacyclin that is currently under clinical trials for the treatment of pulmonary hypertension and vascular disease (excluding renal disease) in North America and Europe.
Beraprost and related benzoprostacyclin analogues of the formula (I) are disclosed in U.S. Pat. No. 5,202,447 and Tetrahedron Lett. 31, 4493 (1990). Furthermore, as described in U.S. Pat. No. 7,345,181, several synthetic methods are known to produce benzoprostacyclin analogues.
Known synthetic methods generally require one or more resolutions of intermediates to obtain the pharmacologically active isomer of beraprost or a related benzoprostacyclin analogue. Also, current pharmaceutical formulations of beraprost or a related benzoprostacyclin analogues may consist of several isomers of the pharmaceutical compound, and only one of which is primarily responsible for the pharmacologic activity of the drug. Isolation of the pharmaceutically active isomer of beraprost compounds from current synthetic methods requires multiple preparative HPLC or chromatographic purification procedures or multiple recrystalizations that are not amenable to a commercially applicable scale. Therefore, it is desired to achieve an efficient, commercially applicable synthetic route to the active isomer of beraprost or a related benzoprostacyclin analogue.